Analysis of the expression patterns of gene induced by abiotic stress and signal in birch.

Heme oxygenase (HO) is the rate-limiting enzyme in the process of heme catabolism which is ubiquitous, sensitive, and highly active . This paper reveals the BpHO expression pattern in signal induction and regulation of secondary metabolism, in an attempt to lay the foundation for the study of gene function in metabolic regulation of birch. In our previous research, the HO gene has been cloned from birch (Betula platyphylla), named BpHO. The molecular structure of BpHO was analyzed by bioinformatics software. Abiotic stress by cadmium (Cd), salt (NaCl) and low temperature (4 ℃), and signal induced by sodium nitroprusside (SNP) and salicylic acid (SA) were used in the study. The expression patterns of BpHO induced by abiotic and signal induction were analyzed. Bioinformatics analysis showed that BpHO is 855 bp, and contains the complete ORF, encoding 284 amino acids (Genebank ID:KJ197335). BpHO is an unstable hydrophobic protein, which does not possess signal peptide and the transmembrane ability either. The alpha helix, extension chain and random coil are distributed throughout the protein. Molecular evolution analysis results showed that the genetic distance of BpHO gene between birch and grape species is relatively close. The gene heredity distance is farther with soybean, Kidney bean and pea, explaining the far genetic relationship with them. Abiotic stress results indicated that BpHO gene expression levels varied with abiotic stress time with fluctuations, but after 6 h treatment BpHO gene for four abiotic stress treatments were up-regulated, indicating BpHO genes are responsive to abiotic stresses. The results suggest that the signal induced by exogenous NO regulates transcription expression of BpHO and the synthesis of heme oxygenase. Salicylic acid is also involved in expression of BpHO. Salt, low temperature, heavy metal, and cadmium stress can promote the expression of BpHO, while the response patterns differ.